Lubricants in commercial use today are prepared from a variety of natural and synthetic base stocks admixed with various additive packages and solvents depending upon their intended application. The base stocks typically include mineral oils, polyalpha-olefins (PAO), gas-to-liquid (GTL) base oils, silicone oils, phosphate esters, diesters, polyol esters, and the like.
A major trend for passenger car engine oils (PCEOs) is an overall improvement in quality as higher quality base stocks become more readily available. Typically the highest quality PCEO products are formulated with base stocks such as PAOs or GTL stocks admixed with various additive packages.
Polyalpha-olefins (PAOs) are important lubricant base stocks with many excellent lubricant properties, including high viscosity index (VI), low volatility and are available in various viscosity range (e.g., kinematic viscosity at 100° C. in the range of 2 to 300 cSt). However, PAOs are paraffinic hydrocarbons with low polarity. This low polarity leads to low solubility and dispersancy for polar additives or sludge generated during service. To compensate for this low polarity, lubricant formulators usually add one or multiple polar co-base stocks. Ester or alkylated naphthalene (AN) is usually present at 1 to 50 wt % levels in many finished lubricant formulations to increase the fluid polarity which improves the solubility of polar additives and sludge. Furthermore, high oxidation stability is generally desirable for a base stock in order to impart a long service life to engine oils.
Aliphatic neo-polyols comprising at least two hydroxyl groups having a common quaternary carbon atom at the beta-location of the hydroxyl groups in the molecule are known. Esters of such neo-polyols featuring multiple ester groups in the molecule have found use as lubricating oil base stocks. They are known for high-temperature oxidation stability. However, they tend to have very high polarity due to the presence of multiple ester groups in the same molecule, causing issues such as seal compatibility to lubricating formulations containing them.
Therefore, there is a need for polar base stock fluids that provide appropriate solubility and dispersancy for polar additives or sludge generated during service of lubricating oils, desired level of polarity, as well as a high oxidation stability.
This disclosure meets this and other needs.